As semiconductor fabrication technologies are continually progressing to smaller feature sizes, immersion lithography apparatus and methods are being adopted. Immersion lithography is a technique that can enhance the resolution of projection lithography by permitting exposures with a numerical aperture (NA) greater than one, which is the theoretical maximum for conventional “dry” systems. By filling the space between a final optical element and a semiconductor wafer, the immersion lithography permits exposure with light that would otherwise be totally internally reflected at an optic-air interface.
When an exposure process is performed using the immersion lithography apparatus, contamination such as particles and water residues may be remained on and thus to contaminate the semiconductor wafer to be processed therein. Such contamination may cause defects and yield degradations of the semiconductor wafers. Accordingly, improvements in immersion lithography apparatus and methods for effective inspection and cleaning of contamination continue to be sought.